Broadcast receiver and channel scanning method

ABSTRACT

A channel scanning method in a multi-channel digital broadcast is provided for enabling a user to identify the broadcast contents of a channel being currently received with accuracy during the channel scan, even though the broadcast contents may change within a channel scanning time period. In one embodiment of the channel scanning method, a receive channel is switched at predetermined intervals (the scanning time period), it is checked whether the broadcast contents of the channel being received currently, after the channel switching, will change within the scanning time period, and a time period for receiving the channel is prolonged, if the broadcast contents will change.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a broadcast receiver and achannel scanning method, and more particularly to a multi-channelbroadcast receiver for switching a receive channel at predeterminedintervals and a channel scanning method using same.

[0003] 2. Description of the Related Art

[0004] In recent years, digital broadcasts have come into service thatconvert broadcast signals into digital signals and compress the digitalsignals to transmit them. Such digital broadcasts have less degradationin sound and image compared with conventional television and radiobroadcasts. The compression of data as described also enables a digitalbroadcast to provide multi-channel broadcasts which handle more than onehundred channels. FIG. 7 is a diagram illustrating the construction of aframe in a digital broadcast. This figure shows that broadcast contentsincluding “n” channels are subjected to mapping (in other words,time-division multiplex) in a frame of a predetermined length. In adigital broadcast, contents of this frame are transmitted in sequence,thereby broadcasting “n” channels simultaneously.

[0005] As described above, digital broadcasts allow a user to select adesired program from much more programs (channels) than the conventionalbroadcast media. In such multi-channel digital broadcasts, a scanningfunction of automatically switching a receive channel at predeterminedintervals is of great value as a method of searching for and selecting adesired channel from multiple channels by the user's simple and easyoperation of keys.

[0006] In a conventional receiver having this scanning function, when achannel scan is instructed by a keystroke of a scan key, the receivechannel is automatically switched to another channel at given intervals(hereinafter referred to as a scanning time period) such as 5 seconds or7 seconds. When a desired channel is found, the broadcast contents ofthe desired channel are continuously received by re-pressing the scankey. In such cases, if the user sets channels belonging to a desiredgenre on a setting screen in advance, the channel scan will be carriedout within the range of the set channels.

[0007] With channel scanning in a conventional receiver, there is a casewhere the broadcast contents of a channel being currently received,after the channel switching, change during the scanning time period. Forexample, one piece of music ends and another piece of music begins onone channel within the scanning time period. When this kind ofchangeover of the broadcast contents occurs, the user cannot accuratelyidentify the broadcast contents or the music provided by the channelbeing currently received. Then, before the user can identify thebroadcast contents, the receive channel is switched to the next channel,thus leading to a disadvantage that the user may miss a program that heor she really wishes to receive (view and/or hear). FIG. 8 explains thiskind of case. Referring to this figure, a channel CH1 which was receivedbefore a time t₁, is switched to a next channel CH2 at the time t₁. Thechannel CH2 changes its broadcast contents M1 to other contents M2 at atime t₂ within a scanning time period Ts after the time t₁. Then thechannel CH2 is also switched to a next channel CH3 at a time t₃. Thus,in a case where the broadcast contents change during the scanning timeperiod, it is difficult to identify the broadcast contents of thechannel being currently received, resulting in a disadvantage that thereceive channel is switched to a next channel before identifying thecurrent broadcast contents thereof.

SUMMARY OF THE INVENTION

[0008] The present invention has been accomplished in view of theabove-mentioned technical background, and it is an object of the presentinvention to realize an improvement which enables a user to identifybroadcast contents of a channel being currently received with accuracy,even though the broadcast contents may change during a scanning timeperiod.

[0009] It is another object of the present invention to realize animprovement which controls a receive channel such that the broadcastcontents of the receive channel do not change within a scanning timeperiod, thereby enabling a user to identify the broadcast contents withcertainty.

[0010] To solve the foregoing problems, according to a first aspect ofthe present invention, there is provided a channel scanning method in amulti-channel broadcast for switching a receive channel at predeterminedtime intervals, comprising: checking whether or not the broadcastcontents of a receive channel being currently received, after thechannel switching, change within the predetermined time interval; andprolonging a time period for receiving the channel, which is beingreceived, in a case where the broadcast contents change. Thus, even ifthe broadcast contents change, the scanning time period is prolonged,thereby allowing the user to identify the current broadcast contentswith accuracy.

[0011] According to a second aspect of the present invention, there isprovided a channel scanning method in a multi-channel broadcast forswitching a receive channel at predetermined time intervals, comprising:extracting information which is transferred together with the broadcastcontents of a next channel to be received and which specifies a time ofa changeover of the broadcast contents; checking whether or not thebroadcast contents of the next channel change within the predeterminedtime interval in the case of switching to the next channel, withreference to the extracted information; and receiving the next channelif the broadcast contents do not change, while repeatedly performing theabove extracting and checking for a further next channel to be receivedif the broadcast contents do change. Thus, the broadcast contents do notchange within the scanning time period, thereby enabling the user toidentify the broadcast contents with certainty.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a diagram showing the construction of a digitalbroadcast receiver according to the present invention.

[0013]FIG. 2 is an explanatory diagram showing the construction of aframe in a digital broadcast.

[0014]FIG. 3 is an explanatory diagram showing the channel scan controlaccording to a first preferred embodiment of the present invention.

[0015]FIG. 4 is a flowchart of the operation of the digital broadcastreceiver according to the first preferred embodiment.

[0016]FIG. 5 is an explanatory diagram showing the channel scan controlaccording to a second preferred embodiment of the present invention.

[0017]FIG. 6 is a flowchart of the operation of the digital broadcastreceiver according to the second preferred embodiment.

[0018]FIG. 7 is a schematic diagram of a frame in a digital broadcast.

[0019]FIG. 8 is an explanatory diagram showing the case where thebroadcast contents change during a scanning time period, in aconventional broadcast receiver.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter some preferred embodiments of the present inventionwill be described in detail with reference to the accompanying drawings.

[0021] (A) Construction of Digital Broadcast Receiver

[0022]FIG. 1 is a diagram showing the construction of a digitalbroadcast receiver according to the present invention. An antenna 1receives broadcast signal radio waves from a satellite. A front end(F/E) section 2 extracts a broadcast signal with a desired receivefrequency component from the broadcast signals received via the antenna1, and frequency-converts the extracted broadcast signal to provide anintermediate frequency signal. A baseband processor 3 comprises aquadrature demodulator 3 a, a forward error correction (FEC) processor 3b, a de-interleave & descramble processor 3 c, and an errordetection/correction processor 3 d. The baseband processor 3 subjectsthe intermediate frequency signal provided from the front end section 2to the quadrature demodulation processing and the FEC (Forward ErrorCorrection) processing. Subsequently, the baseband processor 3 releasesthe de-interleave processing, while descrambling the intermediatefrequency signal to restore it to a previous data string. Finally, thebaseband processor 3 performs the error detection/correction processing(Reed-Solomon decoding processing) to provide high-efficiency code data(MPEG data). A data separator 4 separates each of MPEG video data/MPEGaudio data and information data of the channel, which has been selectedby a user or which has been specified by a scanning function, from thehigh-efficiency code data (MPEG data) of the entire channel providedfrom the baseband processor 3. Thereafter, the data separator 4 providesthe MPEG video data/MPEG audio data to an audio/video decoder 5, and theinformation data to a controller 6 via an information data decoder 13.The audio/video decoder 5 decodes the MPEG video data/MPEG audio datainto an audio signal and a video signal, respectively, to supply theaudio signal to an amplifier 7 and the video signal to an imagesynthesizer 9. Consequently, the audio is provided from a speaker 8,while the video is displayed on a display 10.

[0023] The controller 6 is used to control the overall digital broadcastreceiver, and performs a frequency tuning control of the front endsection 2, an instruction control of the receive channel to the dataseparator 4, and a channel scanning control. Simultaneously, thecontroller 6 creates a menu image for the channel selection on the basisof information about the arrangement of programs received, or creates animage of searched results, to supply the image to the image synthesizer9. The image synthesizer 9 synthesizes the video signal(s) from theaudio/video decoder 5 and the image from the controller 6 to display thesynthesized image on the display 10. An operating section 11 is operableto perform a selecting operation of a channel to be viewed, adesignating operation of a genre of interest upon a search for thegenre, an adjusting operation of volume, an instructing operation of thechannel scan, and the like.

[0024]FIG. 2 is an explanatory diagram showing the construction of aframe in the digital broadcast. This digital broadcasting systemperforms a time division multiplex processing of the broadcast contentsincluding “n” channels into the frame of a predetermined length, andtransmits this time division multiplex frame in sequence, therebysimultaneously broadcasting all n channels. This frame includes data onall channels, namely, channel 1 through channel n. Each channel's dataincludes 1) header data; 2) data on the broadcast contents currentlybeing broadcast (for example, music data if music is being broadcast).The header data includes (1) control information; (2) a label messageLM, and the like. The label message LM includes a service identifier, atotal time period (duration) of the music currently being performed, anelapsed time of the music currently being performed, the name of theartist, the name or title of the music, and so on.

[0025] (B) Channel Scan Control of First Preferred Embodiment

[0026]FIG. 3 is an explanatory diagram showing channel scan controlaccording to a first preferred embodiment of the present invention.

[0027] Referring now to FIG. 3, upon receiving a channel CH1 by the scancontrol and after the time interval set for switching between thechannels, namely, the scanning time period Ts (for example, =5 seconds)has ended, the channel CH1 is switched to a next channel CH2 at a timet₁. Then, upon receiving the channel CH2, if the broadcast contents M1of the CH2 are changed into other broadcast contents M2 at a time t₂within the scanning time period Ts (=5 seconds) after the time t₁, areceiving time period for receiving the channel CH2 is to be prolonged.Specifically, an elapsed time begins to be counted after the channelswitching, and when the broadcast contents of the channel change beforethe scanning time period Ts (=5 seconds) has ended, the elapsed time isreset and the counting of the elapsed time is restarted from zero, sothat the receiving time period is extended. Consequently, as shown inthe example of FIG. 3, the channel CH2 is to be received during afurther scanning time period Ts after the time t₂ (=5 seconds) when thebroadcast contents M1 change into M2. Then at a time t₃, the channel CH2is switched to a next channel CH3, and the channel CH3 is received.Accordingly, the total duration of receiving the channel (CH2) is 8seconds. That is, even though the broadcast contents change during thescanning time period, the total scanning time period is prolonged,thereby allowing the user to identify the broadcast contents withaccuracy.

[0028]FIG. 4 is a flow chart of the operation of the digital broadcastreceiver according to the first preferred embodiment.

[0029] The controller 6 checks whether or not a channel scan has beenrequested by the operation of a scan key (not shown) of the operatingsection 11 (step 101). If requested, a receive channel is determined,and a request for the selection of the determined channel is passed tothe data separator 4 (step 102). Accordingly, the data separator 4extracts the MPEG audio data and the MPEG video data from the requestedchannel to provide the extracted data to the audio/video decoder 5,while providing the information data of the requested channel to thecontroller 6 via the information data decoder 13 (step 103). Thecontroller 6 starts the timer 6 a, so that the timer 6 a counts anelapsed time after the channel switching (step 104).

[0030] Subsequently, the controller 6 checks whether the scanning timeperiod (the time interval set for switching between the channels) Ts hasended or not (step 105). If not, that is, if the scanning time periodhas not ended, it is checked whether a change of the broadcast contents(for example, in a music program, a boundary between two pieces ofmusic) is detected or not (step 106). If a change in broadcast contentsis not detected, the operation returns to step 103, where the channelbeing currently received is to be continuously received, and proceeds tostep 104 and the steps thereafter.

[0031] The change in broadcast contents is detected on the basis ofchecking, for example in the music program, whether the music name ortitle or the artist name included in the label message LB has changed ornot, or on the basis of checking whether the elapsed time of the musicbeing currently performed has reached the total length of the music.

[0032] On the other hand, if a change in broadcast contents is detected,the counting time of the timer 6 a is reset (step 107). The operationthen returns to the step 103, where the channel being currently receivedis to be continuously received, and proceeds to the step 104 and thesteps thereafter. This reset of the counting time prolongs the receivingtime period.

[0033] The operation described above is repeatedly performed, and if thecounting time of the timer 6 a exceeds the scanning time period Ts instep 105, it is checked whether a scan-terminating condition is detectedor not (step 108). If the scan-terminating condition is not detectedyet, the operation returns to step 102 again, and the controller 6requests the reception of a next channel to carry out the proceduresbeginning with step 103.

[0034] In contrast, when the scan-terminating condition is detected instep 108, for instance, the scan key is pressed so as to set a channelfor receiving (viewing and/or listening), the controller 6 terminatesthe channel scanning operation.

[0035] (C) Channel Scan Control of Second Preferred Embodiment

[0036]FIG. 5 is an explanatory diagram showing channel scan controlaccording to a second preferred embodiment of the present invention.

[0037] Referring now to FIG. 5, upon receiving a channel CH1 by the scancontrol, at a time t₁ after the scanning time period Ts (for example, =5seconds) has ended, information for specifying a changeover time t₂ ofthe broadcast contents of a next channel CH2 to be received is extractedfrom the broadcast signal. It is checked whether the broadcast contentsof the channel CH2 will change within the scanning time period Ts (=5seconds) in the case of switching to the channel CH2. FIG. 5 shows theexample where the broadcast contents of the channel CH2 change at a timet₂ within the scanning time period Ts after the time t₁. In this case,the above operation will be performed again as to a further channel CH3to be received. Thereafter, from the above operation, it turns out thatin a case where the channel CH1 is directly switched to the channel CH3,the broadcast contents of the channel CH3 do not change before thescanning time period Ts (=5 seconds) has ended after the time t₁.Accordingly, the channel CH3 is to be received after the channel CH1.

[0038] Upon receiving the channel CH3, at a time t₃ after the scanningtime period Ts (=5 seconds) has ended, information for specifying achangeover time t₂′ of the broadcast contents of the next channel CH2 tobe received is extracted from the broadcast signal. It is checkedwhether the broadcast contents of the channel CH2 will change within thescanning time period Ts (=5 seconds) after the time t₃, in the case ofswitching to the channel CH2. The example of FIG. 5 shows that thebroadcast contents of the channel CH2 do not change within the scanningtime period Ts, namely 5 seconds, after the time t₃. Accordingly, thechannel CH2 is to be received after the channel CH3. Similarly, achannel CH4 is to be received after the channel CH2, in this example.

[0039] In accordance with the operation described above, the broadcastcontents of the channel being currently received never changes withinthe scanning time period, thereby allowing the user to identify thebroadcast contents with certainty.

[0040]FIG. 6 is a flow chart of the operation of the digital broadcastreceiver according to the second preferred embodiment.

[0041] The controller 6 checks whether or not a channel scan has beenrequested by the operation of a scan key (not shown) of the operatingsection 11 (step 201). If requested, a channel to be received isdetermined, and a request for the selection of the determined channelCHi is passed to the data separator 4 (step 202). Accordingly, the dataseparator 4 extracts the MPEG audio data and the MPEG video data of therequested channel CHi to supply the extracted data to the audio/videodecoder 5, while providing information data (such as a label message, orthe like) about the requested channel to the controller 6 via theinformation data decoder 13 (step 203). Subsequently, the controller 6starts the timer 6 a to count an elapsed time after the channelswitching (step 204), while checking whether or not the scanning timeperiod (the time interval set for switching between the channels) Ts hasended (step 205). If the scanning time period has not ended yet, theoperation goes back to step 203 and the steps thereafter, so that thechannel CHi is maintained in a received state.

[0042] On the other hand, if the scanning time period Ts has ended instep 205, it is checked whether or not the scan-terminating condition isdetected (step 206). If the scan-terminating condition is not detected,the controller 6 extracts from the broadcast signals information forspecifying a changeover time of the broadcast contents of a next channelCHi+1 to be received. It is also checked whether the broadcast contentsof the channel CHi+1 will change within the scanning time period Ts (=5seconds) in the case of switching to the channel CHi+1 (step 207).

[0043] The information for specifying the changeover time of thebroadcast contents may be, for example, a stop time of the broadcastcontents being received currently, or a starting time of broadcastcontents to be next received. The stop time of the broadcast contentsbeing received currently is obtained by subtracting an elapsed time ofone piece of music from a total time period of the music, as shown inFIG. 2. The starting time of the next broadcast contents is obtained byadding a time interval t between two pieces of music to the stop timedescribed above. It is noted that the channel data may include the stoptime of the broadcast contents being currently received, the startingtime of the next broadcast contents, and the like.

[0044] If the broadcast contents do not change in step 207, theoperation goes back to step 202 to receive the next channel CHi+1 andproceeds to the steps thereafter. On the other hand, if the broadcastcontents change in step 207, a next channel CHi+2 to be received afterthe channel CHi+1 is determined (step 208), and thereafter the operationproceeds to step 207 again. That is, information for specifying thechangeover time of the broadcast contents of the channel CHi+2 isextracted from the broadcast signal, and it is checked whether thebroadcast contents of the channel CHi+2 will change within the scanningtime period Ts (=5 seconds) in the case of switching to the channelCHi+2.

[0045] The described processes are performed repeatedly, and if thescan-terminating condition is detected in step 206, for example, thescan key is pressed to set the channel for viewing and/or listening, thecontroller 6 terminates the channel scanning operation.

[0046] According to one aspect of the present invention, after thechannel switching, it is checked whether the broadcast contents of achannel being received currently will change within the scanning timeperiod. If so, the time period for receiving the channel is prolonged.Thus, even though the broadcast contents change, the receiving timeperiod, namely, the scanning time period of the channel, is extended,thereby allowing the user to identify the current broadcast contentswith accuracy.

[0047] According to another aspect of the present invention, informationwhich is transmitted together with the broadcast contents of a nextchannel to be received and which specifies a changeover time of thebroadcast contents is extracted, and it is checked whether the broadcastcontents of the next channel will change within the scanning timeperiod, in the case of switching to the next channel, with reference tothe extracted information. If the broadcast contents do not change, thenext channel is to be received. In contrast, if the broadcast contentsdo change, the above operation is performed as to a further channel tobe received. Accordingly, the broadcast contents never change within thescanning time period, thereby enabling the user to recognize thebroadcast contents with certainty.

What is claimed is:
 1. A channel scanning method for switching a receivechannel at predetermined time intervals, comprising: checking whether ornot the broadcast contents of a receive channel being receivedcurrently, after the channel switching, will change within thepredetermined time interval; and prolonging a time period for receivingsaid receive channel, in a case where said broadcast contents willchange.
 2. The channel scanning method according to claim 1, whereininformation transmitted together with and associated with the broadcastcontents is extracted, and said broadcast contents are determined tochange when the contents of said extracted information change.
 3. Thechannel scanning method according to claim 1, wherein an elapsed time ofthe receive channel after the channel switching is counted, and wherein,in a case where the broadcast contents of said receive channel changewithin the predetermined time interval, the elapsed time is reset andcounting of the elapsed time is restarted, thereby prolonging thereceiving time period.
 4. The channel scanning method according to claim2, wherein an elapsed time of the receive channel after the channelswitching is counted, and wherein, in a case where the broadcastcontents of said receive channel change within the predetermined timeinterval, the elapsed time is reset and counting of the elapsed time isrestarted, thereby prolonging the receiving time period.
 5. The channelscanning method according to claim 2, wherein said broadcast contentsinclude a piece of music, and said information associated with thebroadcast contents pertains to one of a music name or title and anartist name.
 6. A channel scanning method for switching a receivechannel at predetermined time intervals, comprising: extractinginformation which is transferred together with the broadcast contents ofa next channel to be received and which specifies a time of a changeoverof said broadcast contents; checking whether or not the broadcastcontents of said next channel will change within the predetermined timeinterval in the case of switching to the next receive channel, withreference to said extracted information; and receiving said next channelif the broadcast contents will not change, while if the broadcastcontents will change, repeatedly performing said extracting and checkingacts for a further channel to be received.
 7. The channel scanningmethod according to claim 6, wherein said information for specifying thechangeover time of the broadcast contents relates to a stop time of saidbroadcast contents, or a starting time of the next broadcast contents.8. The channel scanning method according to claim 6, wherein saidbroadcast contents include a piece of music, and wherein saidinformation for specifying the changeover time of the broadcast contentsis calculated from information on a full-length of the piece of musicand information on an elapsed time of the piece of music being performedcurrently.
 9. A multi-channel broadcast receiver that has a channelscanning function of switching a receive channel at predetermined timeintervals, comprising: means for receiving an instruction to perform achannel scan; receive-channel switching means for performing a channelswitching operation at the predetermined time intervals when theinstruction to perform the channel scan is received; time counting meansfor counting an elapsed time after the channel switching; andreceiving-time-period control means for checking whether or not thebroadcast contents of a receive channel being received currently, afterthe channel switching, will change within the predetermined timeinterval, and for prolonging a time period for receiving said receivechannel, in a case where said broadcast contents will change.
 10. Thebroadcast receiver according to claim 9, further comprising means forextracting information transmitted together with and associated with thebroadcast contents, wherein said receiving-time-period control meansdetermines that said broadcast contents will change when the contents ofsaid information change.
 11. The broadcast receiver according to claim9, wherein said time counting means counts the elapsed time of thereceive channel after the channel switching, and wherein, when thebroadcast contents of said receive channel being received currentlychange within the predetermined time interval, saidreceiving-time-period control means resets the elapsed time and restartscounting of the elapsed time, thereby prolonging the receiving timeperiod.
 12. The broadcast receiver according to claim 10, wherein saidtime counting means counts the elapsed time of the receive channel afterthe channel switching, and wherein, when the broadcast contents of saidreceive channel being received currently change within the predeterminedtime interval, said receiving-time-period control means resets theelapsed time and restarts counting of the elapsed time, therebyprolonging the receiving time period.
 13. The broadcast receiveraccording to claim 10, wherein said broadcast contents include a pieceof music, and said information associated with the broadcast contents isone of a music name or title and an artist name.
 14. A multi-channelbroadcast receiver that has a channel scanning function of switching areceive channel at predetermined time intervals, comprising: means forreceiving an instruction to perform a channel scan; receive-channelswitching means for performing a channel switching operation at thepredetermined time intervals when the instruction to perform the channelscan is received; time counting means for counting an elapsed time afterthe channel switching; means for extracting information which istransferred together with the broadcast contents of a next channel to bereceived and which specifies a time of a changeover of said broadcastcontents; and receive-channel determining means for checking whether ornot said broadcast contents of the next channel will change within thepredetermined time interval in the case of switching to the nextchannel, with reference to said extracted information, and for receivingsaid next channel if the broadcast contents do not change, while if thebroadcast contents will change, repeatedly performing said extractingand checking functions for a further channel to be received.
 15. Thebroadcast receiver according to claim 14, wherein information extractedby said extracting means, which is operable to extract the informationfor specifying the time of the changeover of the broadcast contents,relates to a stop time of said broadcast contents, or a starting time ofthe next broadcast contents.
 16. A multi-channel broadcast receiver thathas a channel scanning function of switching a receive channel atpredetermined time intervals, comprising: a broadcast receiving sectionfor receiving a broadcast wave; an instructing section for receiving aninstruction to perform a channel scan; a time counting section forcounting an elapsed time after the channel switching; and a controllerfor controlling said broadcast receiving section by performing a channelswitching operation at the predetermined time intervals when theinstruction to perform the channel scan is received, for instructingsaid time counting section to count the elapsed time after the channelswitching, for checking whether or not the broadcast contents of areceive channel being received currently, after the channel switching,will change within the predetermined time interval, and for prolonging atime period for receiving said receive channel in a case where saidbroadcast contents will change.
 17. The broadcast receiver according toclaim 16, wherein said broadcast receiving section receives a digitalbroadcast wave.
 18. The broadcast receiver according to claim 17,wherein said controller extracts information associated with andtransmitted together with the broadcast contents, and determines thatsaid broadcast contents change when contents of said information change.19. The broadcast receiver according to claim 18, wherein said broadcastcontents include a piece of music, and said information associated withthe broadcast contents is one of a music name or title and an artistname.
 20. A multi-channel broadcast receiver that has a channel scanningfunction of switching a receive channel at predetermined time intervals,comprising: a broadcast receiving section for receiving a broadcastwave; an instructing section for receiving an instruction to perform achannel scan; a time counting section for counting an elapsed time aftera channel switching; and a controller for controlling said broadcastreceiving section by performing a channel switching operation at thepredetermined time intervals when the instruction to perform the channelscan is received, for referring to information which is transferredtogether with the broadcast contents of a next channel to be receivedand which specifies a time of a changeover of said broadcast contents,for checking whether or not said broadcast contents of the next receivechannel will change within the predetermined time interval in the caseof switching to the next receive channel, and for receiving said nextchannel if the broadcast contents do not change, while if the broadcastcontents will change, repeatedly performing said checking function for afurther channel to be received.